"I've had this problem and in my case it was because the min to max bitrate ratio was too high. "

Ah! Good!


"Played fine on most players but one model would lockup during a camera iris down at the end of a number."

For me , it is where I've invoked the use of some heavy HEAVY TV simulation AND Colour Curves for the Infrared FX - looks cute! However . ..

"There is a program around that'll plot the bitrate and I'll bet you see a huge jump in bitrate where you have the problem."


Ah yes, I remember seeing this too. Anybody have a beed on it?

"Anyway as it's only 20 minutes long why not encode at 8Mb CBR?"

No, Bob, I aint "stuck" on it at all. It was just the first one I grabbed that I know I have had success in past AND using 2-pass for possibly assisting the "noise" factor, I just did. An no, not stuck, just the DVD playing is "stuck". Anyway you have helped me to acknowledge/reconfirm the idea about the MAX:MIN being too far apart.

But yes, I'll have a go at plain vanilla 8, and as I said I'm already doing AC3.

Thank you kind sir.

Yup. Of course success. I ended up going CBR 6. DONE! Played perfectly in Set-top.

Why not CBR 8?
From what you said before you've got some video with a heavy load on the encoder so the more bandwidth the better, so long as you keep it within what the players can cope with and with ac3 you could probably goto CBR 9.

Bob.

PS, check your email.

"Why not CBR 8?"

Well, as I WAS doing another encode I wanted to "see" what the diff would be.

I've received email - from any one I know? You maybe?

Still looking . ..

Yip from me, replied to yours though.
Bob.

. .and when was that, pray?

So the ONLY thing you changed was going from VBR to CBR?? And that one change (nothing else -- same media and exactly, precisely the same video) made it play??

I want to make sure, so I can add this to things I tell people (outside of this forum) to look at when trying to fix compatiblity problems.

4 things.

* VBR to CBR

* 8 MAX to 6 CBR

* NO 2-pass

* Named the file differently so I could identify it.

But Same video and same AC3. In any event I haven't redone the AC3, just kept the same AC3 and slotted in the variations of encoded MPGE2

I've now watched it 4 times on the set-top box, the box that WAS giving me grief, and now it is solid, "Solid as a Rock!"

What can I say?

Bob's point about the "difference" in the RATIO between my MAX - 8 - and my MIN - 0.192 - was too big, to BIG for this particular set-top AND the funky stuff I as pushing through.

I might try and up to 8 CBR and see if I can notice a quality improvement.

What you advise others is up to you. But for my scenario AND applying Bob's experience of a "similar" issue, it is working for me John?

Any DVD that I do below 60 minutes, I make at 8000 CBR. I don't see a need to do VBR unless disk space is a concern. 8 seems to be a safe range for most DVD players and gives you the best quality I think you will see.

Dave T2

As I said in the identical thread in the DVDA forum:

Since you changed to CBR, that muddies it a little. What would be interesting would be to use a bitrate analyzer on the MPEG file that caused the problem and see what the bitrate was doing at the points where you were having problems on the various players. Was it at some peak or valley?

I'd sure like to know for sure, because VBR is something I have to use when doing longer encodes, and I usually leave the max and min at the default settings. However, from what you say in your last post: "MAX - 8 - and my MIN - 0.192 - was too big" those defaults may create a problem. Now, I've sent out discs to many hundreds of different people in the past twelve months and not gotten a single complaint, but I still have anxiety every time I do a project that will be widely distributed, and would love to truly know, scientifically, EVERYTHING I can do to make my disk more compatible.

If Sony's marketing team was really crackerjack, this would be a great project to pursue, and from the knowledge gained, they could write a "white paper" that could really help all of us.

I use some other software sometimes for encoding and authoring. They had a major problem with VBR rates because it used a default that caused some players to pause when fading from black. It seems that the bitrate jump was too much for some DVD players to handle.

Dave T2

John? I said I had gone from VBR to CBR? And this was prior to your first comment here. I really don't see how me reiterating this now makes any difference, or how you can interpret this as, you say, "Since you changed to CBR, that muddies it a little. " - you knew this before too?

All I did was to lower the MAX to 6. I did this so that I could see for myself just what 6 would look like.

As to the BIGness of things, this refers to what Bob was suggesting and saying that the ratio between min and max was too big - the ratio - not the upper or lower setting, but the RATIO between them was too big. Too big for the content on THIS set-top box to cope with. I could have a BIGGER MAX and an incrementally larger MIN, and that would produce the same/similar RATIO. And, not wishing to be further opaque or obdurate in suggesting this, I could also have had a lower MAX and a lower MIN and could have produced a LARGER RATIO. It was the RATIO of the two I understood as coming into play/question. Taking my quote "MAX - 8 - and my MIN - 0.192 - was too big" was and did refer to the size of the RATIO?

I told people I went from VBR to CBR and I was also referring to the size of the RATIO.

Please tell me how I muddied things?

John, I think we/all of us have been here before . .about 5 months back? I think your "scientific" controlled approach is highly commendable. To actually use a piece of software to encounter/register the areas of PEAK is a really fine concept. If you find such software and it is at all at a price that I can meet then let's get going.

I think this is what you need:

http://www.tecoltd.com/bitratev.htm

Problem I'm pretty certain is the players being mechanical devices they have to change speed to match the bitrate and too big a jump and they loose the plot. Even if they don't, the sound of them spinning up and down is a bit distracting so keeping the Min to Max ration at around 1:4 makes sense.

Bob.

TNX Bob - I still don't have an email from yah - mate?

Grazie,
I've sent several, they've not bounced, just obvioulsy not delivered, maybe your spam filter doesn't like me?

Anyway all I was going to do was email you a copy of BV.exe, now I've found the link you can D/L it yourself.

BTW, I'd encourage everyone to BUY the full copy, this guy. like a lot of us, does rely on sales to keep making the product better.

Bob.

Actually Bob, there shouldn't be that kind of speed change on the disk. The rotational rate is fairly constant at any given instant. Yes, the rotational speed will change over time as the disk is read, regardless of whether the disk was written CLV (constant linear velocity) or CAV (constant angular velocity), but the idea is that the disk rotates at a constant velocity.

If you have a low bitrate, then the data just isn't packed as tightly on the disk; high bit rates and the data is packed fairly close.

The only time you would encounter significant mechanical speed changes in a short time period would be if the error rate from the disk was very high, and the reader was trying to get a better read by slowing down the rotational speed.

--Scott

I doubt the "data packing" changes at all. A thousand bits is gonna take the same linear space on the disc no matter what the current bit rate is. To create a burning algorithm that spaces the bits out during lower bit rate sections of the video would be impractical at best and fraught with errors.

The player can cache at least a rotation's worth of data. If the video stream slows down then the player will just hang out on that track while the disc keeps spinning until it needs to move on to the next track. The only time that the drive would spin down at all is if the player doesn't need any new data for an extended period of time, probably at least 5 seconds or more. The idle pauses due to low bit rates are probably on the order of microseconds at most.

I'm not expressing myself well. The bottom line is that the DVD player is not constantly speeding up or slowing down the rotational speed of the DVD based on the current bitrate of the MPEG data stream. Yes, the rotational speed does change as we move from the cener of the DVD outward, but not because of the MPEG bitrate.

--Scott

the rotational speed does change as we move from the center of the DVD outward, but not because of the MPEG bitrate.

Exactly so. The data is buffered and the disc should, in theory, only change rotational speed (angular velocity) in order to make the pits on the disc go by the laser at the same speed. Thus, the disc will rotate more slowly when the laser is focused on the outside edge of the DVD, and rotate rather quickly when the laser is over the part of the disc nearest the hub. All disk drives (hard disks, CD-ROM, DVD drives, etc.) have a RAM memory buffer so that the mechanical mechanisms don't have to thrash themselves apart trying to track the instantaneous changes in data demands. The data gets read in at a constant rate. If the buffer fills up because the computer can't take the data fast enough, then the disk rotates for awhile until some of the data in the buffer is read out.

Some observations:

This for the SUCCESSFUL CBR 6
• I have a peak of 7.811 close to end of video – why? If set at 6 why “allow” a peak of 7.811 ( that’s almost 8?!?)

• Around the point of the area at issue – 10:30 > 11:21 – there are 4 major spikes and very quickly followed by major troughs.

Here are the spikes and timings:

Br
6.823 @ 10:30
6.964 @ 10:52
6.839 @ 11:07
6.884 @ 11:21



And now for the UNSUCCESSFUL recipe - VBR Mx8 AVB 5.4 Min 0.192

• Although AVB was set to 5.4 I have 4.9 reflected in the calculator.

• I have a peak of 7.874 close to end of video, followed by a trough of 0.207

• Around the point of the area at issue – 10:30 > 11:21 – there are 4 major spikes and very quickly followed by major troughs.

Here is on of the spikes/trough timings:
Trough 0.808 @ 10:33
Spike 7.7272 @ 10:35

And from here on in the “difference” between the Bitrate Level and the Quantise (Q) level separates markedly

10:52 > Q = 4.77 Br = 6.170
10:53 > Q = 11.78 Br = 5.792
10:56 > Q = 10.54 Br = 4.597

comes closer together here
11:03 > Q = 4.96 Br = 4.983

and THEN in the next 4 seconds separates dramatically:

11:05 > Q = 8.14 Br = 5.215
11:06 > Q = 7.73 Br = 4.773
11:07 > Q = 9.43 Br = 5.194
11:08 > Q = 17.52 Br = 5.168
11:09 > Q = 19.50 Br = 5.317


Do I understand that the “Quantize” figures refers to what is ACTUALLY happening on screen? And the Bitrate figures are those that the MPEG is supplying?

It would appear that when I use VBR plus some MASSIVE Q values, the MPEG values don’t appear to want to follow or create a value near to the MAX ( viz: Q = 19.50 and Br = 5.317 ) and for several seconds prior to this peak too.

However when I “crunched” it to CBR 6.0 I get more even/level Br values even over the problematic region - reflected by the vast changes in material on screen. But this works. Big disparaity in Br and Q values, but the video plays.

I’m making my own conclusions as a result of doing this PITA analysis – but I’ll wait for the maths Gurus to say something.

Learned Gentlemen, I beg to differ!

Firstly a CD / DVD is not the same as a hard disk, there is only one continuous track, the head doesn't jump from one track to the next.

Secondly whilst the RPM may change to keep CAV I suspect it's not quite that simple:

We can fill a DVD with 1 hour of video or 4 hours of video by changing the bitrate. This means the head has to traverse the same length of track (this is fixed when the DVD is made) in 1 hour or 4 hours.

Now I doubt there's a 4 to 1 difference in rotational speed between those scenarios however something has to give, I seriously doubt the drive can buffer that much data. Rather I suspect based on observation that the drive simply stops spinning until the buffer empties. When I say 'observation' I can hear the drive change speed, quite possibly it's going from zero to some predetermined rate, I can't say for sure but it certainly doesn't just sit there spinning the whole time. Furthermore those changes are correlated to observed changes in bitrate, 5 seconds of true black followed by 100% noise will cause a drive to stop (or slow down) and then start (or speedup) if you set the minimum bitrate low enough and the maximum bitrate high enough.

Now playing a DVD in a PC reveals much the same thing, during extended periods of very low bitrate the access LED on the drive goes out and when it comes to a section of high bitrate the LED goes on again and I sure can hear the drive making some sound that sounds for all the world like a spinning thing accelerating.

Furthermore (sorry again) it's at these very points that some players simply loose the plot and stop playing the video. Now by good chance on more than one DVD I've had a chapter marker bang in the middle of that extended period of 100% black. The player will play from the marker perfectly, probably because subsequent to that point there's a very slow fade up to pretty clean video. The prior fade down was quick and from very noisy video and this seems to be what triggered the problem.

I could be completely wrong but so far all my theories fit the observed facts, i.e. DVD drives don't just keep spinning regardless of the data they're reading, at least not when they're playing a DVD.

Bob.

Bob .. what do you think of that work I did with BV? - huh . . ?